1. Field of the Invention
The present invention relates generally to the fields of cytokine biology and therapeutic applications of cytokines. More specifically, the present invention relates to uses of the novel cytokine TRANK.
2. Description of the Related Art
Most living organisms have evolved several antioxidant proteins and peptides to counteract the damaging effects of reactive oxygen species. These include superoxide dismutase, glutathione, glutaredoxin, thioredoxin, thioredoxin reductase and thioredoxin peroxidase. Most of these proteins have been well conserved during evolution (1, 2). Almost all antioxidant proteins are cytoplasmic proteins, and can thus only protect those cells producing them.
Natural killer cell-enhancing factor (NKEF) is a protein that was discovered recently and has been found to possess antioxidant properties that protect proteins and DNA from oxidative damage (3). NKEF is a 24-kDa protein that was initially found to be abundant in red blood cells and to augment natural killer (NK) cell-mediated cytotoxicity (4). This protein is encoded by two distinct genes, nkef-A and nkef-B, which are 71% identical in their nucleotide sequence and 88% identical in their deduced amino acid sequence (5).
nkef-B is a gene for thioredoxin peroxidase, and transfection of cells with this gene can block apoptosis (19). Similarly, overexpression of another thioredoxin peroxidase gene, AOE372, blocked the activation of the nuclear transcription factor kappa B (NF-xcexaB) and degradation of the inhibitory subunit of NF-xcexaB, IxcexaBxcex1, induced by tumor necrosis factor (TNF) and phorbol ester (2). This is consistent with the antioxidant properties of the protein product of this gene (1).
Activation of NF-xcexaB is induced by many agents, such as inflammatory cytokines (e.g., tumor necrosis factor (TNF), lymphotoxin (LT), and interleukin (IL)-1), mitogens, bacterial products, protein synthesis inhibitors, H2O2-induced oxidative stress, ultraviolet light, and phorbol esters. The inhibition of NF-xcexaB is an important step in the treatment of various pathological conditions which result from the activation of NF-xcexaB by these agents. Substances which can inhibit the activation of NF-xcexaB may be used for therapeutic treatment for pathological conditions including toxic/septic shock, graft vs. host reaction, acute inflammatory conditions, acute phase response, viral infection, radiation damage susceptibility, atherosclerosis, and cancer.
Also important in the consideration of the effects of activation of NF-xcexaB are downstream gene products, most prominently inducible nitric oxide synthase (iNOS) and intracellular adhesion molecule-1 (ICAM-1). iNOS is one of the major enzymes involved in the synthesis of nitric oxide (NO), a highly reactive free radical. It has emerged as an important mediator of inflammatory responses. For example, tumor necrosis factor (TNF), in combination with nitric oxide and/or other cytokines (such as interleukin-1 and interleukin-6), may bring about the tissue destruction observed in certain autoimmune diseases such as psoriasis, rheumatoid arthritis, osteoarthritis and other joint diseases.
On a physiological level, nitric oxide is the most potent vasodilator known and is required for a variety of cellular functions. For example, the cytotoxic activity of macrophages is dependent on nitric oxide. The production of nitric oxide in the vascular endothelium regulates blood pressure, and it is a neurotransmitter. Clearly, nitric oxide has beneficial biological functions that serve a variety of physiological processes, however, it also has less salutary effects. nitric oxide is unstable and it inhibits enzymes; intracellular nitric oxide is highly reactive and reacts with other free radicals, molecular oxygen and heavy metals. Persistent high concentrations of nitric oxide can cause DNA damage.
The role of nitric oxide in pathophysiology is thus suggested, but its precise dimensions are not clear. Although nitric oxide might in some way modulate tumor development, it has been unclear whether it inhibits or stimulates tumor growth, angiogenesis or metastasis. With respect to the role of nitric oxide in cancer, it has been observed that breast cancer cell lines, human breast cancer cells and mouse mammary tumor cell lines produce nitric oxide in amounts that correlate with tumor grade. Breast cancer tissue samples have been shown to express iNOS in the infiltrating macrophages of the tumor. Further, p53 expression down-regulates iNOS expression. Additionally, nitric oxide itself directly affects the regulation of p53 gene expression as well as the conformation and activity of the p53 protein. It is possible that nitric oxide induces mutations in p53 that abrogate iNOS regulation, and these could contribute to cell transformation. Excessive nitric oxide production in inflamed tissues might play a role in carcinogenesis by impairing the tumor suppressor function of p53. Further, there have been conflicting reports indicating that nitric oxide can stimulate or inhibit angiogenesis.
Hence, modulation of nitric oxide levels via control of iNOS expression as regulated by NF-xcexaB activation could have far-reaching physiological implications. The prior art is deficient in the description of the uses of secretory cytokines to manipulate NF-xcexaB activation, which may play an important role in inflammatory processes and cellular pathophysiology. The present invention, methods for the control of NF-xcexaB functions by use of a novel secretory cytokine, TRANK, fulfills this long-standing need and desire in the art.
A novel cytokine polypeptide, termed TRANK, has been previously described (22). This protein is secreted by cells, has a molecular weight of approximately 30 kDa on SDS-PAGE and is further characterized by activation of the nuclear transcription factor NF-xcexaB and downstream gene products (e.g. iNOS or ICAM-1), as well as the activation of c-Jun N-terminal kinase (JNK). Additionally, TRANK has proliferative effects on normal human foreskin fibroblasts.
In one embodiment of the present invention, there is provided a process for utilizing the novel TRANK polypeptide for therapeutic purposes. Examples of such purposes include the stimulation of production of iNOS or ICAM-1 or inhibition of NF-xcexaB or JNK via antibody technology.
In other embodiments of the present invention, there are provided pharmaceutical compositions of TRANK and methods of treating conditions in which insufficient levels of such NF-xcexaB-dependent gene products as iNOS or ICAM-1 are present, comprising the administration of an effective dose of TRANK.
In yet another embodiment of the present invention, there is provided a method for the inhibition of nuclear transcription factor NF-xcexaB for use in the treatment of pathological conditions including toxic/septic shock, graft vs. host reaction, acute inflammatory conditions, acute phase response, viral infection, radiation damage susceptibility, atherosclerosis, and cancer, comprising the step of administering an anti-TRANK antibody to an individual in need of such treatment.
In another embodiment of the present invention, there is provided a method for the inhibition of the synthesis of nitric oxide by inhibiting NF-xcexaB and a downstream gene products, iNOS.
Other and further aspects, features, and advantages of the present invention will be apparent from the following description of the presently preferred embodiments of the invention. These embodiments are given for the purpose of disclosure.